Speed of Light discredites TEDx talks?

Rupert Sheldrake argued that speed of light is dropping!

“In an effort to keep ahead of the intellectual tide, they’ve started incorporated substandard speakers, including woomeisters, and have spawned “TEDx,” local versions of TED talks.

The TEDx talk at Whitechapel by Rupert Sheldrake gave Deepak Chopra a run for the title of World’s Biggest Woomeister.

I’ve written about Sheldrake before—about his antimaterialistic views.

His ideas that dogs finding their way home, or people knowing that others are watching them behind their backs, proves Jesus; his weakness for telepathy and other bizarre mental phenomena; and his general attitude that science is DOING IT WRONG by hewing to materialism and avoiding the numinous and spiritual (you can find some of my posts here, here, and here)

It’s all on view in this talk: anti-materialism, the narrow dogmatism of scientists, his view that inanimate things have consciousness, and his most bizarre idea: “morphic resonance,” a quasi-Jungian view that all members of a species share in a collective memory, so if you train a rat in Chicago it will make rats in Tokyo more trainable. The talk is meant to flog his new book The Science Delusion, which I won’t link to.

One thing that Sheldrake said got my notice: his argument that the speed of light has dropped from 1928-1945, and that this drop was almost certainly a real drop in that supposedly invariant value rather than just measurement error or refinements in measurement technology. This supports Sheldrake’s renegade view that the “laws of nature” aren’t constant.

I wrote Sean Carroll, our Official Website Physicist™, asking him about this speed-of-light business. Here’s his response, printed with permission:

The speed of light stuff is a non-kerfuffle, obviously. There’s a plot on this page of measurements over time:

There was a small shift in the central value around 1947, approximately the size of the error bars at the time. Nothing that would cause a non-agenda-driven person to give it a second glance.

What the crackpots don’t understand is that

(1) scientists would love to find that the speed of light has been changing, they’d be giving out Nobel prizes like Halloween candy; and

(2) in some sense, the speed of light can‘t change.

It’s a dimensional quantity — it can only change relative to something else, and there aren’t any other absolute velocities in physics. (Indeed, today the speed of light is fixed by definition, not by measurement.)

What people really mean when they talk about measuring changes in the speed of light is measuring changes in other related quantities, like the fine-structure constant or the mass of the electron. And there are better ways of constraining those than by measuring light propagation.

Thanks, Sean! And TED, you’d better vet your speakers from now on.

Note: I belive that “Speed of light is fixed by definition, not by measurement”. And I wonder:

1. Why all these measurements since 1878? And how with such accuracy?

2. And how could scientist get the idea of measuring the speed of light before Einstein deduced it by a succession of integrals from the traditional energy equation, assuming that mass is also a quantity that varies with time?